Heat exchangers are commonly made from multiple stacked plate pairs which define coolant flow passages extending between a pair of headers. As shown in FIG. 1 of U.S. Pat. No. 6,273,183 issued on Aug. 14, 2001 to So et al., the plates of each pair are arranged in back-to-back relation and are joined together at their peripheral edges. The plates have raised central portions which define a flow passage therebetween and in which turbulizers may be located. Raised bosses are provided at the ends of the plates, and are apertured to provide inlet and outlet openings. When the heat exchanger is assembled, the bosses are aligned and in communication with one another thereby forming a pair of headers. Expanded metal fins may then be located between the plate pairs to allow another fluid, such as air, to flow transversely through the plate pairs. The raised end bosses also serve to create spaces between the plate pairs for insertion of the fins.
The individual plates making up such a heat exchanger are usually formed by a process known as “progressive stamping” in which the plates are progressively formed by successive stamping operations performed on a coil of sheet metal. As explained above, the end bosses must be of a sufficient height to allow insertion of cooling fins. The bosses must also be of a specific diameter or area to allow sufficient coolant flow through the headers. Thus, the strip width required for each plate is generally determined by the width of strip material required for formation of the bosses.
In many cases, the width of strip material required to form the bosses is greater than a desired width of the plate pairs. This results in the need to trim excess material along the edges of the plates, particularly between the end portions in which the bosses are formed. The amount of scrap material generated by conventional progressive stamping of heat exchanger plates can be as high as 35 percent.
Thus, there is a need for improved methods of forming heat exchanger plates in which generation of scrap is reduced or eliminated, and in which plates of varying lengths may be produced without excessive tooling costs.